PubMed Health⌕ Search

Biomedical subjects

A Gali

Publications and source records attributed to A Gali.

5 recordsLinked to original sources
PubMed2006

Identification of the carbon antisite-vacancy pair in 4H-SiC.

The metastability of vacancies was theoretically predicted for several compound semiconductors alongside their transformation into the antisite-vacancy pair counterpart; however, no experiment to date has unambiguously confirmed the existence of antisite-vacancy pairs. Using electron paramagnetic resonance and first principles calculations we identify the S15 center as the carbon antisite-vacancy pair in the negative charge state (C(Si)V-(C)) in 4H-SiC. We suggest that this defect is a strong carrier-compensating center in n-type or high-purity semi-insulating SiC.

Journal Article↗
PubMed2006

Divacancy in 4H-SiC.

Electron paramagnetic resonance and ab initio supercell calculations suggest that the P6/P7 centers, which were previously assigned to the photoexcited triplet states of the carbon vacancy-antisite pairs in the double positive charge state, are related to the triplet ground states of the neutral divacancy. The spin density is found to be located mainly on three nearest C neighbors of the silicon vacancy, whereas it is negligible on the nearest Si neighbors of the carbon vacancy.

Journal Article↗
PubMed2000

Overcoordinated hydrogens in the carbon vacancy: donor centers of SiC

Epitaxial silicon carbide is likely to contain hydrogen and vacancies ( V); therefore, V+nH complexes are likely to influence its electronic properties. Using ab initio calculations we show that neutral and positive H atoms are trapped by carbon vacancies ( V(C)) in three-center bonds with two Si neighbors. The double positive charge state of V(C)+H is not stable in equilibrium and in the triply positive state H binds only to one of the Si neighbors. At most two H atoms can be accommodated by a single V(C). The V(C)+nH complexes have donor character and exhibit rather atypical vibration modes for Si-H bonds. Occupation levels and spin distributions were calculated and compared for V(C)+H and V(C).

Journal Article↗
PubMed1991

Human hydatidosis in Niger.

Thirty-two cases of hydatidosis were collected in two Nigerian hospitals during a 5-year period; 81% of these had extra-hepatic localizations. Human hydatidosis has been considered as exceptional in West Africa but seems to be an underestimated disease in Niger. Studies in slaughtered animals from Niger show a high prevalence of hydatidosis in camels while no infection was found among sheep.

Adolescent↗